- During the escalation phase, tumor biopsies will be optional and will be evaluated for pharmacodynamic (PD) studies for evidence of Wee1 inhibition DNA damage and repair, and apoptosis (yH2AX, pNbs1, Rad51, pTyr15-Cdk and caspase 3). During the expansion phase, once MTD is reached, mandatory paired tumor biopsies will be pursued in up to 20 additional patients enrolled at the MTD to further evaluate PD endpoints.